Shadow tomography of quantum states with prediction

The shadow tomography problem introduced by [1] is an important problem in quantum computing. Given an unknown n-qubit quantum state ρ, the goal is to estimate tr(F_1ρ),…,(F_Mρ) using as least copies of ρ as possible, within an additive error of ε, where F₁,…,F_M are known 2-outcome measurements. In this paper, we consider the shadow tomography problem with a potentially inaccurate prediction ϱ of the true state ρ. This corresponds to practical cases where we possess prior knowledge of the unknown state. For example, in quantum verification or calibration, we may be aware of the quantum state that the quantum device is expected to generate. However, the actual state it generates may have deviations. We introduce an algorithm with sample complexity Õ(n max{∥ρ − ϱ∥₁,ε}log²M/ε⁴). In the generic case, even if the prediction can be arbitrarily bad, our algorithm has the same complexity as the best algorithm without prediction [2]. At the same time, as the prediction quality improves, the sample complexity can be reduced smoothly to Õ(nlog²M/ε³) when the trace distance between the prediction and the unknown state is Θ(ε). Furthermore, we conduct numerical experiments to validate our theoretical analysis. The experiments are constructed to simulate noisy quantum circuits that reflect possible real scenarios in quantum verification or calibration. Notably, our algorithm outperforms the previous work without prediction in most settings.